This invention relates to a tension member for belt used in various kinds of belts and a power transmission belt using the same.
A power transmission belt such as a synchronous belt, a V-belt, a flat belt and a ribbed belt requires a high strength, a high modulus of elasticity and a high dimensional stability. To satisfy these required properties, reinforcements such as a reinforcing cord made of fibers and a reinforcing fabric are embedded in a body of the power transmission belt. Such reinforcements are generally formed with the use of a twist yarn formed in a way of twisting a plurality of fiber strands. Twist yarns are classified, by twisting manner, under several types such as a piled yarn, a single twist yarn and a Lang's twist yarn.
Such a power transmission belt using the twist yarn as a tension member may not sufficiently respond to the demands of the market for higher durability, dimensional stability and the like. To cope with this, there is proposed a technique in which a tension member is formed of a braided cord instead of a twist yarn (See Japanese Patent Application Laid-Open Gazettes Nos. 3-211041, 3-213747 and 3-244848).
However, the demands of the market on a power transmission belt have extended to an increasingly higher level in recent years and the power transmission belt is used under the hostile conditions of a high load, a high temperature and the like. In consideration of this, it is desired to improve the tension member formed of the above-mentioned braided cord.
An object of the present invention is to improve a braided cord as a tension member for power transmission belt thereby increasing the flex fatigue resistance of the belt.